Homogeneous reactions catalysed by transition metals, allowing formation of carbon-carbon bonds, are considered to be important synthetic methods. One example thereof is the olefin metathesis reaction, which has proved its efficiency in the synthesis of high-molecular-weight polymers as well as the synthesis of medicines or other materials. Metal alkylidene complexes, notably molybdenum complexes, have shown good activities in homogeneous olefin metathesis reactions, even in the presence of various functional groups, and these performances greatly depend on the other ligands present around the metal. By way of example, R. R. Schrock's work can be mentioned, who compared the activities of many molybdenum and tungsten imidocarb complexes for the homometathesis of 1-octene (Organometallics, 2009, 28 (1), 355-360).
In 2002, Martyn P. Coles' group proved that the (R2BO)− and (RBO2)2− ligands could be coordinated to a metal such as molybdenum (J. Chem. Soc., Dalton Trans., 2002, 4168-4174) or zirconium to form novel complexes (Inorg. Chem., 2002, 41 (13), 3548-3552). These ligands provide steric and electronic effects that are different from their carbon-containing homologs.
We have discovered novel group 6 organometallic complexes having one or more boron-containing ligands bonded to the metal via a heteroatom. These complexes have the specific feature of being active as catalysts in olefin metathesis reactions.